On Mar 17, 7:38*am, Jim Wilkins wrote:

In the presence of U-Boote how would British subs communicate that
they were friendly to attacking British destroyers?

They wouldn't be able to. However, it is very unlikely that the
British destroyers would be worrying that much about U-boats. Their
best defense against U-boats would be speed: by moving fast (which
they will want to do anyway to avoid all those Luftwaffe planes, to
find and bring to battle the KM forces, and even to tip over the
invasion barges with their bow waves) they won't give submerged
submarines much of a chance to get into position: unless the submarine
is already in the correct position they won't be able to engage.

The KM invasion forces, on the other hand, will be tied to the 3-4
knot invasion barges, so there will be a lot of slow, tempting targets
for the RN submarines.

Chris Manteuffel